The goal of this project is to identify how aging causes tissue functional and structural declines. These studies are being performed using the nematode, C. elegans, which offers both genetic and cell biological approaches for studying this problem. In C. elegans, aging affects locomotory ability much more dramatically than sensory ability, which is relatively well-maintained during aging. The basis for this age-related locomotory deficit appears to be due, at least in part, to functional declines in the muscles. A second aim of this project is to investigate the basis for aging-related decline of the pharynx, a small, isolated neuromuscular organ in the head of the animal. In the pharynx, aging appears to primarily affect the muscle's ability to respond to neuronal stimulation, and probably does not significantly affect neuronal function. In addition, we demonstrated that muscle contraction is a major contributor to functional declines in this organ during aging. Furthermore, pharynx functional decline could be separated from functional decline in locomotory muscles